DE69807032T2 - OPHTALMIC LENS GENERATING DEVICE WITH VIBRATION DAMPING ARRANGEMENT - Google Patents

Abstract

An ophthalmic lens generating apparatus having a tool spindle comprising a motor, a lens surfacing tool and a coupling mounted between the motor and the lens surfacing tool for retaining the lens surfacing tool to the arbor of the motor. The apparatus of the present invention also comprises a first actuated table supporting the tool spindle in a movable manner along the longitudinal axis of the apparatus. A massive base is mounted beneath the first actuated table for supporting the table and for dampening radial vibrations of the tool spindle. The apparatus further comprises a lens holder for holding an ophthalmic lens in a plane substantially perpendicular to the longitudinal axis of the apparatus. A massive upright block is mounted on one end of the massive base behind the structural support supporting the lens holder, for dampening axial vibrations of the tool spindle and of the lens holder. The coupling of the tool spindle is a kinematic coupling having first and second disks having each substantial mass and radius of gyration. Thus, when the tool spindle rotates, both disks increase the nominal moment of inertia of the spindle and dampen the torsional vibrations of the spindle.

Description

This invention relates to an ophthalmic lens forming apparatus, and more particularly, the present invention relates to a lens forming apparatus with vibration damping properties.

The surface finishing of ophthalmic lenses is fundamentally affected by two known types of surface defects inherent in machined lens finishing. The first type of defect is caused by the actual removal of material from the lens surface, and the second type is caused by the vibration of one or more machine elements.

The main factors affecting the surface defects of the first type are the contour of the cutting tool in contact with the lens, the microstructure and chemical bonding of the lens material and thermal effects occurring during the material removal process. In this context, improvements in surface finish can be achieved to varying degrees by increasing the cutting speed, lowering the cutting feed and changing the cutting fluid and tool geometry.

Surface defects of the first type generally have surface irregularities of relatively small dimensions, usually less than 2 microns peak-to-valley. These surface defects are usually overall converging through a clear resin coating as is well known in the art of lens manufacturing.

However, vibration of machine elements is often the cause of deeper irregularities on the surface of the produced lenses. Vibration of machine elements is very complex and often involves a combination of interrelated causes, as explained below.

Rotating machines are generally known to vibrate according to three basic types of vibration. A first basic type of vibration is caused, for example, by unbalanced tools, eccentricity in the tool clamping device and defects in a drive belt. This first type of vibration has an amplitude in the radial direction relative to the axis of rotation of the tool.

The second basic type of vibration in rotating machines has an amplitude in the axial direction along the axis of rotation of, for example, the tool spindle. This axial vibration is often caused by a fluctuating plane of rotation of the cutting side of the tool or by intermittent cutting forces. Since the cutting force acting on a tool has a vector component in the axial direction, a vibration of the radial type also tends to cause vibration in the axial direction.

The third type of vibration in rotating machinery is torsional vibration. This type of vibration is often associated with torque pulses associated with types of some electric motors and motor controllers. These pulses tend to alternately increase and decrease the amount of material removed from the lens surface during a full rotation of the tool. When cutting forces are present, this torsional vibration is known to cause vibrations of the radial and axial types.

From the theory of vibration analysis it is also known that each of the three vibration types mentioned above is a resonance condition of the machine structure with the consequence of an increasing amplitude of the vibrating element.

The problem of vibration of a lens manufacturing apparatus has been addressed in part in the past. For example, in US Patent 4,434,581 a first apparatus for manufacturing ophthalmic lenses is described which discloses an apparatus of the type according to the preamble of the main claim. This apparatus comprises tables with X-Y fluid bearings mounted on a granite support weighing approximately 1814 kg. This support is undoubtedly partially suitable for reducing the amplitude of vibration in the radial direction, that is in a direction perpendicular to the table. It will be appreciated, however, that a heavy table is less suitable for reducing vibrations of the axial and torsional types where the lens holder or tool spindle is mounted at some distance from the surface of this table.

In another example, U.S. Patent 4,760,672 to Darcangelo et al., issued August 2, 1988, describes a lens grinding and polishing apparatus in which a drive motor is mounted remotely from the tool support table and drives a micrometer drive via a drive belt. This type of mounting isolates the tool and work spindle from the vibrations of the drive motor.

Although the devices in both of the above examples are particularly suited to dampening the radial vibrations of the tool and the holding spindles, these devices, like other known optical lens manufacturing devices, lack vibration damping properties in the axial and circumferential directions with respect to the rotatable tool and the tool holder.

In the present invention, the apparatus for producing an optical surface on an ophthalmic lens is provided with a base, a tool spindle including a motor and a lens surface machining tool rotatably coupled to the motor for rotation by the motor, a first actuatable linear sliding means mounted on the base, and a first movable support means attached to the tool spindle for movable Supporting the tool spindle along a longitudinal axis and a lens holder for retaining an ophthalmic lens having a circumference substantially perpendicular to the longitudinal axis and characterized by heavy block means connected to the lens holder which extends along an axis and is longitudinally immovable relative to the base for vibration damping in a clamping means which forms part of the lens holder in a direction parallel to the longitudinal axis.

In one aspect of the present invention, the ophthalmic lens manufacturing apparatus includes a tool spindle having a motor, a lens surface finishing tool, and a clutch mounted between the motor and the lens surface finishing tool for retaining the lens surface finishing tool on a shaft of the motor. The apparatus also includes a first operable table mounted below the tool spindle for supporting the tool spindle in a movable manner along the longitudinal axis of the apparatus. The heavy base is mounted between the first operable table for supporting the table and for dampening the tool spindle having a displacement in a direction substantially perpendicular to the longitudinal axis of the apparatus.

The apparatus may comprise a lens holder having clamping means and structural lens holder support means for holding an ophthalmic lens in a plane substantially perpendicular to the longitudinal axis of the apparatus. A heavy upright block is mounted on the heavy base behind the structural lens holder support means for supporting the structural lens holder support means and for dampening the tool spindle and lens holder which has a displacement in a direction substantially parallel to the longitudinal axis of the apparatus. Computerized control means are also provided for operating the spindle and the first movable table and for moving the lens surface finishing tool along a prescribed path relative to the lens holder.

The most important advantage of the device of the present invention is that the optical surface produced thereon is invariably smooth. The Ophthalmic lenses produced by the present invention have a machined surface that is optically acceptable and no further polishing is required.

In another aspect of the present invention, the tool spindle has a nominal moment of inertia about an axis of rotation thereto, and the coupling is a kinematic coupling comprising first and second circular disks. The first and second circular disks have a corresponding mass and radius of rotation, both disks increasing the nominal moment of inertia of the spindle as the tool spindle rotates about its axis of rotation and improving damping of the torsional vibrations of the spindle.

As will be explained later, radial vibration of a lens grinding tool is essentially tangential to the lens surface being produced. This type of vibration leaves only superficial impressions on a lens surface. However, axial vibration is essentially perpendicular to the lens surface and contributes greatly to the roughness of the lens surface. Similarly, torsional vibrations coupled with axial vibrations tend to form circular recesses that are detrimental to producing high quality optical lens surfaces.

Other features of the invention are apparent from the dependent claims and specific description of such a device given below. The invention also includes a method for minimizing vibrations when using a device for producing an optical surface on an ophthalmic lens, the device including a lens holder for holding a lens with a circumference of the lens substantially perpendicular to a longitudinal axis and a tool spindle with a motor and a lens surface finishing tool rotatably coupled to the motor, the lens surface finishing tool being movable with the motor linearly along the longitudinal axis and in a precise path transverse to the longitudinal axis, wherein for use of the device

(i) the ophthalmic lens is held in the lens holder and

(ii) a lens processing portion of a rotating lens surface processing tool is moved along a path corresponding to a predetermined curvature of the ophthalmic lens; and the method is characterized by

(iii) damping vibrations in a clamping means forming part of the lens holder having an amplitude in a direction substantially perpendicular to the ophthalmic lens using a heavy blocking means together with the lens holder extending transversely to the longitudinal axis and longitudinally immobile relative to the base of the device.

While the damping of axial and torsional vibrations in ophthalmic lens manufacturing apparatus has been substantially controlled in the past, the apparatus of the present invention includes a damping structure to reduce the influence of most of the known types of vibrations found in rotating machinery. The ophthalmic lens manufacturing apparatus of the present invention includes a plurality of vibration damping masses arranged together to absorb the radial, axial and torsional vibrations of the elements of the apparatus. As a result, an optically acceptable final surface finish is achievable with a single operation.

The preferred embodiment of the present invention will be further understood from the following description with reference to the drawings in which:

Fig. 1 is a top and left side perspective view of the ophthalmic lens forming apparatus of the preferred embodiment;

Fig. 2 is a plan view of the ophthalmic lens forming apparatus of the preferred embodiment;

Fig. 3 is a partial sectional view of a left side of the ophthalmic lens forming apparatus of the preferred embodiment taken along line 3-3 in Fig. 2;

Fig. 4 is an exploded side view of the elements of the tool spindle of the ophthalmic lens forming apparatus of the preferred embodiment,

Figure 5 is a side perspective view of the lens surface tool of the ophthalmic lens forming apparatus of the preferred embodiment;

Fig. 6 is a schematic view of a typical

lens surface treatment;

Fig. 7 is a vector diagram illustrating the forces present during lens surface treatment;

Fig. 8 shows a first type of dynamic vibration isolator;

Fig. 9 is a cross-sectional view taken along line 9 in Fig. 8, illustrating a cylindrical auxiliary mass;

Fig. 10 shows a second type of dynamic vibration absorber; and

Fig. 11 is a cross-sectional view taken along line 11 in Fig. 10, illustrating an annular auxiliary mass.

The ophthalmic lens production device of the preferred embodiment is shown in its entirety in Figs. 1, 2 and 3. The device of the preferred embodiment has a tool spindle 20 which is mounted on a support structure which has at least two degrees of freedom. The tool spindle 20 is mounted on a turntable 22 which can rotate about a vertical Axis is pivotable substantially along the illustrated Z-axis in a direction designated α in Fig. 2. The turntable 22 is mounted on a base plate 24 which is movable on a first, linearly actuable carriage 26 along the longitudinal axis of the device. The longitudinal axis is generally referred to as the X-axis of the device.

A lens holder 30 is also supported on a movable mounting plate 32. The mounting plate 32 includes a portion of a second linearly actuated carriage 34' which is slidably housed in a third linearly actuated carriage 36. The second linear carriage 34', which includes moving the mounting plate 32 up and down along the Z axis and the third linear carriage 36, moves the plate 32 transversely relative to the longitudinal axis of the device along the generally designated Y axis.

The lens holder 30 may also be rotatable about an axis parallel to the longitudinal axis by means of a rotary actuator (not shown) for the purpose of angularly positioning a lens as required by a regulation prior to the lens surface forming process.

All of the linear slides 26, 34' and 36 are preferably mounted on high precision fluid pressure bearings. Similarly, the turntable 22 and the tool spindle 20 are also preferably mounted on high precision fluid bearings. Since such bearings are essentially well known types of bearings, they are not shown.

The movements of the actuated linear slides and actuated turntable are controlled by a computer (not shown) according to the requirements of a prescription for the lens being manufactured. During operation of the ophthalmic lens manufacturing apparatus of the preferred embodiment, the tool spindle 20 advances against the lens along the X-axis and pivots about the Z-axis in a clockwise direction when the apparatus is viewed from above. The lens holder 30 moves along the Y-axis simultaneously with the movement of the tool spindle 20 so that an arc along the edge of the tool describes a predetermined curve over the surface of the lens. The arc along the edge of the tool and the predetermined curvature define a toric surface on the lens.

The ophthalmic lens making apparatus of the preferred embodiment also includes a solid granite base 40 which contributes significantly to the overall rigidity and stability of the machine. The granite base 40 is particularly effective in absorbing the vibrations of the tool spindle 20 and the lens holder 30 in a radial direction relative to the spindle and holder, and the mass of the base 40 must be of sufficient magnitude for this purpose.

The structure of the apparatus of the preferred embodiment also includes a heavy upright granite block 42 which supports the third linear slide 36. The primary purpose of this upright granite block 42 is to absorb vibrations of the lens holder 30 and the tool spindle 20 in the axial direction relative to the lens holder 30, and the block 42 must have an adequate mass for this purpose. The upright granite block 42 is attached to the granite base 40 by means of through bolts 44 as shown in Fig. 3.

Representative preferred properties for the heavy granite base 40 and the heavy granite upright block 42 are as follows:

Granite base: 81.3 cm wide x 152.4 cm long x 20.3 cm thick; it has a total weight of 697 kg.

Upright granite block: 78.7 cm wide x 70.0 cm high x 35.6 cm thick; it has a total weight of 472 kg.

Referring now to Figures 4 and 5, the tool spindle of the lens forming apparatus of the preferred embodiment is shown. The main elements of the tool spindle 20 are: the cutting tool 50, the circular head plate 52, and the spindle drive motor 54. The cutting tool 50 includes a cup-shaped body 56 having at least two cutting inserts 58 formed of a material containing tungsten carbide or similar material. The cup-shaped body 56 is mounted on a circular disk plate 60 having means 62 for positioning within mating recesses 64 on the circular head plate 52 and coupling the circular head plate 52.

The cutting tool 50 also includes a torsion bar 66 that extends through the head plate 52 and couples a locking sleeve (not shown) mounted within the rotor shaft or core of the spindle drive motor 54. This type of tool mounting assembly is referred to herein as a kinematic coupling and is described in US-A-5678967. The tool mounting assembly maintains the axis of rotation of the cutting tool coaxial with the axis of rotation of the rotating motor shaft.

The tool 50 shown in Figure 5 is preferably adjusted for high precision characterized by a total peak-to-valley displacement of 25 nanometers when this tool is rotating at an operating speed at a speed of approximately between 7,000 and 10,000 RPM.

The advantage of using a cutting tool with kinematic coupling is primarily to enable quick and precise tool changes on the tool spindle 20. More importantly, the tool and kinematic coupling comprise a first large circular disk plate 60 and a second circular head plate 52 having a correspondingly large moment of inertia for absorbing torsional vibrations of the tool spindle 20. Preferably, the disk plate 60 has a moment of inertia which, expressed in weight units, is approximately 26.34 kg-cm² and the head plate 52 has a moment of inertia expressed in weight units of approximately 70.23 kg-cm².

The spindle drive motor 54 is also selected to have as large a moment of inertia as is practical. The tool spindle 20 of the ophthalmic lens generator of the preferred embodiment is characterized by the magnitude of the following representative moments of inertia. The spindle drive motor 54 with the head plate 52 has a moment of inertia expressed in units of weight of 205.1 kg-cm2 and the moment of inertia of a typical cutting tool 50 with a disk plate 60 is 33.07 kg-cm2.

Referring to Figures 6 and 7, there is shown a vectorial representation of the forces and vibrations present during lens formation in operation. The radial vibrations of the rotating spindle are indicated by the arrow labeled "R". The axial vibrations are indicated by an arrow labeled "A", and the torsional vibrations are indicated by the arrow labeled "α".

The radial vibrations "R" are in a direction substantially perpendicular to the axis of rotation of the tool. The axial vibrations "A" are in a direction along the axis of rotation of the tool, and the torsional vibrations are in an angular direction relative to the axis of rotation of the tool 50.

Likewise, the vectorial representation of Figure 7 represents the forces present during the removal of material from the surface of the lens 72. The cutting force "F" is substantially perpendicular to the cutting edge of the tool. The force "F" has a radial component "FR" in the feed direction and an axial component "FA" in an axial direction relative to the axis of rotation of the tool 50.

The magnitude of the cutting force "F" and its components "FR" and "FA" are proportional to the feed rate and the cutting depth of the cutting insert 70. Therefore, when a radial, axial or torsional vibration interrupts the connection of the tool 50, both the radial "FR" and the axial "FA" components are inevitably affected.

In light of the foregoing, it will be understood that any vibration in the radial, axial or circumferential direction relative to the tool spindle has a direct effect on the magnitude of the cutting forces. Since a certain degree of elasticity is found in most machine structures, variations in the cutting forces are often accompanied by microscopic deflections of the elements of the device and are more or less transmitted into the material being removed from the surface of the lens.

It will also be appreciated that radial vibrations are translated into dominant radial forces "FR" oriented in a plane which is essentially tangential to the surface of the lens. Therefore, the bends associated with the fluctuations in the radial forces "FR" have a relatively shallow depth. The bends associated with the fluctuations in the axial forces "FA", however, have a deeper dimension and contribute greatly to the optical quality of a produced lens.

As noted above, the apparatus of the preferred embodiment includes a heavy granite upright block 42 to increase the rigidity of the structure that supports the lens holder 30 and absorbs the axial vibrations of the tool spindle 20 and lens holder 30. The tool spindle 20 of the apparatus of the preferred embodiment has a large moment of inertia, effectively reducing any fluctuations in the angular velocity of the tool spindle to imperceptible levels. Thus, the masses of the base 40, the upright block 42, and the moment of inertia of the tool spindle 20 cooperate to reduce the overall vibration of the elements of the apparatus. Most importantly, the masses of the upright block 42 and spindle 20 cooperate to reduce the axial vibrations of the tool 50 and lens holder 30.

The operation of the ophthalmic lens producing apparatus of the preferred embodiment is characterized by remarkable smoothness, producing a high quality optical surface in a single operation. The ophthalmic lenses produced thereon do not require further polishing. Surface roughness measurements of less than 1 micron are substantially consistently achievable in lenses produced by the apparatus of the preferred embodiment. A surface roughness measurement is defined as the arithmetic mean of the dimensional deviation from the best-matched surface of the lens.

As a further disclosure, the circular head plate 52 and the circular disk plate 60 each have sufficient dimensions for adapted dynamic vibration dampers, such as those shown in Figures 8 through 11. Dynamic vibration dampers are often referred to as additional mass dampers in the art of vibration analysis and are used to reduce the torsional or angular vibrations in rotating elements. Although quantitative results for the application of these dampers to the tool spindle 20 of the apparatus of the preferred embodiment are not yet available, it is believed that the optical surfaces produced by the apparatus of the preferred embodiment can be further improved by the use of such accessories.

A first proposed model of a dynamic damper is shown in Figures 8 and 9. A circular disk plate 60' has a series of vibration dampers, each having a cylindrical mass 80 loosely confined in a through-bore 82 in the disk plate 60'. Each cylindrical mass 80 has a circular recess 84 around its cylindrical surface for mating with a circular rib 86 around the inner surface of the through-bore 82 so that the cylindrical mass 80 is maintained in coplanar alignment with the circular plate 60'.

A second proposed type of dynamic damper compatible with the shape of the circular head plate 52 or the circular disc plate 60 is shown in Figs. 10 and 11. In this example, a circular disc plate 60" has a recess around a collar area. An annular mass 90 is resiliently mounted in this recess by means of a layer of soft rubber 88 or similar resilient material so that the annular mass 90 can absorb fluctuations in the peripheral speed of the disc plate 60".

Although dynamic vibration dampers are described in this way and their effects on reducing torsional vibrations are known in the field of vibration analysis and rotating machinery, the prior art lens forming apparatus does not include such adapted devices. However, the tool spindle 20 of the apparatus of the preferred embodiment includes a circular head plate 52 and a circular disk plate 600, and the dampers may advantageously be included pre-assembled.

While the above description provides a thorough and complete disclosure of the preferred embodiment of this invention, various Modifications, alternative constructions and equivalents may be provided without departing from the scope of the invention. Such changes may include alternative materials, components, structural arrangements, sizes, design features or the like. Therefore, the above description and illustrations should not be construed as a limitation on the scope of the invention which is defined by the appended claims.

Claims (23)

1. Device for producing an optical surface on an ophthalmic lens with a base (40), a tool spindle (20) which includes a motor (54) and a tool (50) for processing the lens surface, which tool is rotatably coupled to the motor for rotation by the motor, a first actuatable linear sliding means (26) mounted on the base and with a first movable support means (24) attached to the tool spindle for movably supporting the tool spindle (20) along a longitudinal axis (x) and a lens holder (30) for retaining an ophthalmic lens (72) with a substantially perpendicular circumference to the longitudinal axis (x) and characterized by heavy block means (42) connected to the lens holder (30) which extends along an axis (x) and longitudinally immovable relative to the base (40) for vibration damping in a clamping means which forms part of the lens holder (30) in a direction parallel to the longitudinal axis (x). 2. Device according to claim 1, characterized in that the base (40) is heavy in order to dampen vibrations of the tool spindle (20) and of a part of the lens holder (30) forming the clamping in a direction substantially oblique to the longitudinal axis (x). 3. Device according to claim 1 or 2, characterized in that the tool spindle (20) has a first circular body (60) for mounting on a rotatable shaft of the motor (54), which has a moment of inertia of a satisfactory size in order to dampen torsional vibrations of the tool spindle (20). 4. Device according to claim 3, characterized in that the tool spindle (20) has a second circular body (52) for mounting on a rotatable shaft of the motor (54), which has a moment of inertia of a satisfactory size in order to further dampen torsional vibrations of the tool spindle (20). 5. Apparatus according to claim 4, characterized in that the tool spindle (20) further includes coupling means (66) for removably coupling the lens surface finishing tool (50) to a rotatable shaft of the motor (54) and that the first and second circular bodies are integral components of the coupling means (66). 6. Device according to claim 6, characterized in that the coupling means (66) is a kinematic type coupling. 7. Device according to one of claims 4 to 6, characterized in that at least one of the first and second bodies comprises an auxiliary mass damper (80, 90) for additionally damping torsional vibrations of the tool spindle (20). 8. Device according to one of claims 1 to 7, characterized in that the heavy base (40) is a flat, rectangular element mounted below the first actuatable linear slide means (26), and that the heavy block means (42) is an upright block mounted on the base (40) and extending transversely to one end of the base (40). 9. Device according to claim 8, characterized in that the base (40) and the heavy block means (42) are made of granite and have a weight of approximately 680 kg and approximately 450 kg respectively. 10. Device according to one of claims 1 to 9, characterized in that the total moment of inertia of the tool spindle (20) is expressed in weight units of at least 241.3 kg-cm². 11. Device according to one of the preceding claims, characterized in that the tool (50) for lens surface processing is a circular, cup-shaped tool for lens surface processing; the first actuatable linear sliding means (26) and the support means (24) include an actuatable rotary element (22) having a rotation axis perpendicular to the longitudinal axis (x) for adjustably angling an operating axis of the tool spindle (20) relative to the longitudinal axis; the lens holder (30) includes a second actuatable linear sliding means (34) secured to the heavy block means (42) and the lens holder (30) for moving the lens (72) in a direction (2) perpendicular to the longitudinal axis (x); and wherein the first and second actuatable linear slide means and the rotary member are simultaneously actuatable such that the above-described path and an arc on the lens surface finishing tool contacting the lens cooperate to define a toric surface on the lens during the lens forming process. 12. Device according to claim 11, characterized in that the first (26) and the second (34') actuatable linear sliding means include pressure fluid bearings. 13. Apparatus for producing an optical surface on an ophthalmic lens as claimed in claim 11 or 12, characterized in that the circular cup-shaped tool (50) has circumferentially mounted cutting inserts (58) suitable for an operating speed between about 7,500 RPM and about 10,000 RPM and has a dynamic equilibrium at operating speed characterized by a total radial runout of about 0.025 microns. 14. Device according to one of the preceding claims, characterized by a third actuatable linear sliding means (36) with an oblique horizontal axis (Y) which extends perpendicularly relative to the longitudinal and vertical axes wherein the third linear sliding means is connected to the heavy block means (42) and to the second linear sliding means (34) for movably supporting the second linear sliding means along the oblique horizontal axis relative to the heavy block means. 15. A method for minimizing vibrations when using a device for producing an optical surface on an ophthalmic lens, the device including a lens holder (30) for holding the lens (72) on a circumference of the lens that is substantially perpendicular to a longitudinal axis (x), and a tool spindle (20) with a motor (54) and a tool (50) for processing the lens surface that is rotatably coupled to the motor, the tool for processing the lens surface being movable with the motor linearly along the longitudinal axis and a precise path transverse to the longitudinal axis, wherein for using the device (i) the ophthalmic lens is held in the lens holder (30) and (ii) a lens processing portion of a rotatable lens surface processing tool (50) is moved along a path corresponding to a predetermined curvature of the ophthalmic lens; and the method is characterized by (iii) dampening vibrations in a clamping means forming part of the lens holder (30) having an amplitude in a direction substantially perpendicular to the ophthalmic lens by using a heavy blocking means (42) in connection with the lens holder (30) which extends transversely to the longitudinal axis (x) and longitudinally immovable relative to the base (40) of the device. 16. The method according to claim 15, characterized by the additional step of damping torsional vibrations of the rotating tool (50) for lens surface processing. 17. Method according to claim 15 or 16, characterized by the additional step of damping radial vibrations of the rotating tool for lens surface processing and the clamping means. 18. The method of claim 15, 16 or 17 wherein: Step (iii) is accomplished by attaching an upright, heavy block means (42) to the lens holder to extend transversely to the longitudinal axis, the upright, heavy block means being a longitudinally immovable part of the device and dampening vibrations of the lens holder in the longitudinal direction. 19. A method according to claim 15, 16, 17 or 18, characterized by the further step of securing the tool spindle (20) to a heavy base block means spaced from and extending along the longitudinal axis to damage vibrations of the tool spindle and the lens holder obliquely to the longitudinal direction. 20. A method according to claim 19, characterized by immovably attaching the upright, heavy block means to the heavy base block means. 21. A method according to claim 20, characterized in that the upright, heavy block means is a granite block having a weight of approximately 450 kg. 22. A method according to claim 21, characterized in that the heavy base block means is a granite block having a weight of approximately 680 kg. 23. Method according to one of claims 16, 17, 18, 19, 20, 21 or 22, characterized in that the damping of the torsional vibrations of the rotating tool (50) for lens surface processing is achieved by providing a motor with a rotatable shaft connected to the tool spindle.